The present invention is directed to an attachment assembly formed of an anchor bolt and expansion wedge where the anchor bolt has an outside surface widening in a wedge-type shape manner at its leading end in the setting direction and forms a wedge surface along which the expansion wedge can be displaced in the setting direction for effecting the expansion of the assembly. The anchor bolt has a flange-like engagement part for applying a load located in its trailing end region. The engagement part has a throughbore for receiving the expansion wedge, wherein the expansion wedge is held in the pre-assembled state to the anchor bolt.
Attachment assemblies formed of an anchor bolt and expansion wedge are used mainly for securing intermediate ceilings, paneling, framework, pipes, cables and the like. Since these attachment assemblies are used in large quantities, they must be manufactured economically and must be set with only a small expenditure of time and without the use of special tools. The attachment assemblies are formed in such a way that one part is shaped as an anchoring bolt and serves to receive a load to be carried by the assembly. An expansion wedge can be displaced axially along a wedge surface on the anchor bolt in all of the known attachment assemblies. After the expansion has been effected, the attachment assembly is secured tightly in a prepared receiving bore, for instance, in a ceiling. If a force is applied to the anchor bolt, for instance, by a suspended load, an additional after-expansion of the attachment assembly takes place.
An attachment assembly is disclosed in EP-A-0,283,720 made up of an anchor bolt and expansion wedge. The anchor bolt has a wedge surface along which the expansion wedge can be displaced in the setting direction for expanding the attachment assembly, as well as an engagement part flange with a throughbore for guiding the expansion wedge. The expansion wedge has two projections which, during pre-assembly of the attachment assembly, that is, while assembling the anchor bolt and expansion wedge, serve for securing the expansion wedge relative to the anchor bolt in the throughbore. The projections extend at least partially radially beyond the surface of the throughbore in the engagement flange and are subjected, during the preliminary assembly of the expansion wedge in the anchor bolt, to a slight deformation due to the blocking process, when the projections in the setting direction of the attachment assembly come into contact with the surface of the throughbore in the engagement flange. In such an arrangement, the expansion wedge can tilt, so that its setting side and lifts off and becomes remote from the anchor bolt while projecting radially beyond the outside surface of the anchor bolt. An attachment assembly pre-assembled in such a way often cannot be inserted into a prepared receiving borehole, matched to the diameter of the anchor bolt, because of the remote portion of the expansion wedge. A disadvantage of such a known attachment assembly is that, in particular, when inserting it into a receiving bore in a ceiling, a self-induced retention or holding of the attachment assembly in the bore is not assured. Therefore, the operator must make sure up to the end of the setting stamp, that the attachment assembly is seated correctly in the receiving bore.
To remedy these disadvantages, it is proposed in EP-A-0620 347 to use an attachment assembly formed of an anchor bolt and an expansion wedge, where the expansion wedge is shaped arcuately, so that in the unexpanded state it only contacts the surface of the anchor bolt at a front end region and a rear end region. During preassembly, the expansion wedge of this proposed attachment assembly is displaced along the anchor bolt. The leading end region of the expansion wedge slides, at least partially, along the wedge surface of the anchor bolt. In this unexpanded position, the expansion wedge is secured to the anchor bolt by means of the flange-like part whereby the leading end region of the expansion wedge rests at the wedge surface of the anchor bolt. During insertion of this attachment assembly into a receiving bore matched to the diameter of the anchor bolt, a reverse deformation of the outwardly curved or arcuately shaped expansion wedge takes place. As a result, a pre-stressing force acting in the radial direction is developed with the attachment assembly retained in the receiving bore and particularly simplifies an overhead installation. While it is possible to counter the disadvantages of the previously known attachment assemblies in this way, even this attachment assembly can be further improved.
The expansion wedge in the improved attachment assembly is provided with a region of reduced wall thickness, so that during the setting process, a rear region of the expansion wedge can move forwardly relative to the front region, during the setting procedure, whereby the trailing end of the expansion wedge can be set so that its surface is flush with the flange-like engagement part. In hard concrete, the expansion forces of the receiving bore are often so high that the expansion wedge is sheared off during the driving process in the region of the reduced wall thickness acting as a rated shearing point. The special configuration of the shearing point permits the continued driving of the expansion wedge. When the shearing action takes place, the expansion wedge no longer is properly supported in the receiving bore and it may drop out of the throughbore. While this situation has no negative effect on the retention properties of the attachment assembly, it can cause problems for the tool operator if he determines that there is no longer a solid support in the receiving bore for the portion of the expansion wedge visible to him, or that portion drops out of the throughbore.